teach /proc/$pid/numa_maps about transparent hugepages

commit 32ef43848f283e0ef945d3c67e851c143fea3970 upstream.

This is modeled after the smaps code.

It detects transparent hugepages and then does a single gather_stats()
for the page as a whole.  This has two benifits:
 1. It is more efficient since it does many pages in a single shot.
 2. It does not have to break down the huge page.

Signed-off-by: Dave Hansen <dave@linux.vnet.ibm.com>
Acked-by: Hugh Dickins <hughd@google.com>
Acked-by: David Rientjes <rientjes@google.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
index 9dca07e..5afaa58 100644 (file)
--- a/fs/proc/task_mmu.c
+++ b/fs/proc/task_mmu.c
@@ -936,6 +936,26 @@ static int gather_pte_stats(pmd_t *pmd, unsigned long addr,
        pte_t *pte;
 
        md = walk->private;
+       spin_lock(&walk->mm->page_table_lock);
+       if (pmd_trans_huge(*pmd)) {
+               if (pmd_trans_splitting(*pmd)) {
+                       spin_unlock(&walk->mm->page_table_lock);
+                       wait_split_huge_page(md->vma->anon_vma, pmd);
+               } else {
+                       pte_t huge_pte = *(pte_t *)pmd;
+                       struct page *page;
+
+                       page = can_gather_numa_stats(huge_pte, md->vma, addr);
+                       if (page)
+                               gather_stats(page, md, pte_dirty(huge_pte),
+                                               HPAGE_PMD_SIZE/PAGE_SIZE);
+                       spin_unlock(&walk->mm->page_table_lock);
+                       return 0;
+               }
+       } else {
+               spin_unlock(&walk->mm->page_table_lock);
+       }
+
        orig_pte = pte = pte_offset_map_lock(walk->mm, pmd, addr, &ptl);
        do {
                struct page *page = can_gather_numa_stats(*pte, md->vma, addr);